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Remove Tx model

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There was a split between a transaction request and an actual
transaction. This was kind of annoying because transactions were one-way
only, while transaction requests were two-way - which is what I believe
most transactions will be using. Tx model has been removed and the
responsibilities of it are covered by TxRequest. It simplifies
everything surrounding transactions, since we have only one model to
deal with instead of two.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>
This commit is contained in:
Alek Ratzloff
2020-03-26 12:49:46 -04:00
parent 80ad39eb6f
commit c320f81181
7 changed files with 101 additions and 171 deletions
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153
trading/models.py
View File

@@ -3,6 +3,7 @@ from typing import Mapping, Optional, Sequence
from django.conf import settings
from django.contrib.auth.models import AbstractBaseUser, PermissionsMixin
from django.db import models
from django.db.models import Q
from django.db.models.signals import post_save, pre_save
from django.dispatch import receiver
from django.utils.translation import gettext_lazy as _
@@ -76,38 +77,56 @@ class User(PermissionsMixin, AbstractBaseUser):
def balances(self) -> Mapping["Commodity", int]:
from django.db.models import Sum
credits = {
row["commodity"]: row["amount__sum"]
for row in self.credits.values("commodity").annotate(Sum("amount"))
# We are the source, receiving from the destination
credits_sent = {
row["dest_sends"]: row["dest_amount__sum"]
for row in self.tx_sent.filter(status=TxRequest.ACCEPTED)
.values("dest_sends")
.annotate(Sum("dest_amount"))
}
debits = {
row["commodity"]: row["amount__sum"]
for row in self.debits.values("commodity").annotate(Sum("amount"))
# We are the destination, accepting from the source
credits_received = {
row["source_sends"]: row["source_amount__sum"]
for row in self.tx_received.filter(status=TxRequest.ACCEPTED)
.values("source_sends")
.annotate(Sum("source_amount"))
}
# We are the source, sending to the destination
debits_sent = {
row["source_sends"]: row["source_amount__sum"]
for row in self.tx_sent.filter(~Q(status=TxRequest.DECLINED))
.values("source_sends")
.annotate(Sum("source_amount"))
}
# We are the desination, purchasing from the source
debits_received = {
row["dest_sends"]: row["dest_amount__sum"]
for row in self.tx_received.filter(status=TxRequest.ACCEPTED)
.values("dest_sends")
.annotate(Sum("dest_amount"))
}
ipos = {
row["pk"]: row["in_circulation"]
for row in self.commodity_set.values("pk", "in_circulation")
}
tx_requests = {
row["source_sends"]: row["source_amount__sum"]
for row in self.transaction_requests_sent.filter(status=TxRequest.OPEN)
.values("source_sends")
.annotate(Sum("source_amount"))
}
keys = (
set(ipos.keys())
| set(credits.keys())
| set(debits.keys())
| set(tx_requests.keys())
| set(credits_sent.keys())
| set(credits_received.keys())
| set(debits_sent.keys())
| set(debits_received.keys())
# | set(tx_requests.keys())
)
return frozendict(
[
(
Commodity.objects.get(pk=pk),
credits.get(pk, 0)
credits_sent.get(pk, 0)
+ credits_received.get(pk, 0)
+ ipos.get(pk, 0)
- debits.get(pk, 0)
- tx_requests.get(pk, 0),
- debits_sent.get(pk, 0)
- debits_received.get(pk, 0)
# - tx_requests.get(pk, 0),
)
for pk in keys
]
@@ -179,40 +198,6 @@ class MaxCommodityError(Exception):
super().__init__("maximum commodity count reached")
class Tx(models.Model):
"""
A transaction from one account to another.
"""
id = HashidAutoField(primary_key=True)
instant = models.DateTimeField(auto_now_add=True, editable=False)
source = models.ForeignKey(
User,
on_delete=models.PROTECT,
related_name="debits",
related_query_name="debit_tx",
verbose_name=_("source"),
editable=False,
)
dest = models.ForeignKey(
User,
on_delete=models.PROTECT,
related_name="credits",
related_query_name="credit_tx",
verbose_name=_("destination"),
editable=False,
)
amount = models.PositiveIntegerField(verbose_name=_("amount"), editable=False)
commodity = models.ForeignKey(Commodity, on_delete=models.PROTECT, editable=False)
request = models.ForeignKey(
"TxRequest", null=True, default=None, on_delete=models.SET_NULL
)
class Meta:
verbose_name = _("transaction")
verbose_name_plural = _("transactions")
class TxRequest(models.Model):
"""
A transaction request between two users.
@@ -230,6 +215,7 @@ class TxRequest(models.Model):
(ACCEPTED, "Accepted"),
]
id = HashidAutoField(primary_key=True)
status = models.CharField(
max_length=max([len(c) for c in STATUS_CHOICES]),
choices=STATUS_CHOICES,
@@ -245,23 +231,25 @@ class TxRequest(models.Model):
# )
source = models.ForeignKey(
User,
on_delete=models.CASCADE,
related_name="transaction_requests_sent",
editable=False,
User, on_delete=models.CASCADE, related_name="tx_sent", editable=False,
)
dest = models.ForeignKey(
User,
on_delete=models.CASCADE,
related_name="transaction_requests_received",
editable=False,
User, on_delete=models.CASCADE, related_name="tx_received", editable=False,
)
source_sends = models.ForeignKey(
Commodity, on_delete=models.CASCADE, related_name="+", null=True, editable=False,
Commodity,
on_delete=models.CASCADE,
related_name="+",
null=True,
editable=False,
)
dest_sends = models.ForeignKey(
Commodity, on_delete=models.CASCADE, related_name="+", null=True, editable=False,
Commodity,
on_delete=models.CASCADE,
related_name="+",
null=True,
editable=False,
)
source_amount = models.PositiveIntegerField(editable=False)
@@ -304,7 +292,6 @@ class TxRequest(models.Model):
dest_balance = self.dest.balance_of(self.dest_sends)
return self.status == TxRequest.OPEN and dest_balance >= self.dest_amount
def accept(self):
"""
Accepts an open transaction request.
@@ -320,28 +307,6 @@ class TxRequest(models.Model):
# Update status
self.status = TxRequest.ACCEPTED
# Create source transaction
source_tx = Tx.objects.create(
source=self.source,
dest=self.dest,
amount=self.source_amount,
commodity=self.source_sends,
request=self,
)
# Create dest transaction
dest_tx = Tx.objects.create(
source=self.dest,
dest=self.source,
amount=self.dest_amount,
commodity=self.dest_sends,
request=self,
)
# Save everything
source_tx.save()
dest_tx.save()
self.save()
def decline(self):
@@ -353,8 +318,6 @@ class TxRequest(models.Model):
self.save()
class BalanceError(Exception):
def __init__(
self, balance: int, source: User, dest: User, amount: int, commodity: Commodity
@@ -367,22 +330,24 @@ class BalanceError(Exception):
super().__init__("balance too low to create transaction")
@receiver(pre_save, sender=Tx)
def _tx_pre_save(sender, instance, *args, **kwargs):
@receiver(pre_save, sender=TxRequest)
def __tx_pre_save(sender, instance, *args, **kwargs):
"""
Ensures that a transaction cannot be created if the source user doesn't have enough of the given
commodity in their account.
"""
if instance.pk is None:
balance = instance.source.balance_of(instance.commodity)
if instance.amount > balance:
source_balance = instance.source.balance_of(instance.source_sends)
if instance.source_amount > source_balance:
raise BalanceError(
balance,
source_balance,
instance.source,
instance.dest,
instance.amount,
instance.commodity,
instance.source_amount,
instance.source_sends,
)
# Do not check dest balance - could be a side channel for determining another account's
# funds which is not something we want
@receiver(post_save, sender=TxRequest)